Arylsulfonyl halides, such as, for example, benzenesulfonyl chloride, are particularly useful as intermediates in the manufacture of certain biologically active compounds and as polymer plasticizers. For example, benzenesulfonyl chlorides can be reacted with primary or secondary amines to produce certain arylsulfonamides such as, for example, N-(beta-0,0-diisopropyl-dithiophosphorylethyl) benzenesulfonamide and N-butyl benzenesulfonamide, a nylon plasticizer.
These arylsulfonyl halides can be produced by many methods. For instance, a commonly employed procedure is the reaction of an arylsulfonic acid with either thionyl chloride or phosphorus pentachloride. Other processes include the reaction of an arylsulfonic acid with thionyl chloride in the presence of a sulfonating agent (U.S. Pat. No. 4,105,692), and the reaction of an arylsulfonic acid with a carbonyl halide in the presence of dimethylformamide and a tertiary amine (U.S. Pat. No. 3,795,705). In Yet another method, arylsulfonic acid is reacted with a sulfur monohalide in the presence of excess halogen. This latter method is especially useful in the production of benzenesulfonyl chloride wherein benzenesulfonic acid, sulfur monochloride and chlorine are reacted to produce benzenesulfonyl chloride. In this process described immediately above, the arylsulfonyl halides produced can be removed by distillation from the reaction mixture. However, the distilled arylsulfonyl halide product is usually discolored by the presence of impurities and can be almost black in color. It would be advantageous from a customer's viewpoint to treat the arylsulfonyl halide with various decolorizing agents to achieve a pale yellow to colorless product of higher purity.